An opto-isolator is a device that transfers a signal optically between two electrical circuits operating at different electrical potentials while, at the same time, electromagnetically isolating the circuits from each other. Opto-isolators also isolate one part of a system from electrical noise in another part of the system and protect circuits against damage from voltage surges. A transmitter module of the opto-isolator comprises an electrical-to-optical converter (EOC), such as a visible or infrared light emitting diode (LED), for example, that converts an electrical driver signal into an optical signal. A receiver module of the opto-isolator comprises an optical-to-electrical converter (OEC), such as a photodiode, for example, that converts the optical signal back into an electrical signal.
An optical waveguide optically couples the transmitter and receiver modules to each other to allow optical signals produced by the EOC of the transmitter module to be transmitted to the OEC of the receiver module. The optical waveguide is typically a length of optical fiber, but other optical waveguides are sometimes used for this purpose. For example, it is known to use an optically transmissive rod as the optical waveguide surrounded by a fluid having a refractive index that is different from the refractive index of the rod.
Although these types of optical waveguides generally work well at coupling optical signals between the transmitter and receiver modules while also providing electrical isolation, they are relatively costly to implement. A need exists for an opto-isolator that utilizes a less costly, yet optically efficient, optical waveguide for coupling optical signals between the transmitter and receiver modules of the opto-isolator while also providing sufficient electrical isolation.